Field
Aspects of the present invention generally relate to a power transmission device, a power transmission method, and a storage medium.
Description of the Related Art
Conventionally, a technique for supplying power in a non-contact manner (wirelessly) has been known. Examples of systems for supplying power in a non-contact manner include four systems: an electromagnetic induction system, a magnetic field resonance system, an electric field coupling system, and a radio wave reception system. Among these systems, the magnetic field resonance system is characterized in that it can transmit a sufficiently large amount of power with a long transmission distance. Consequently, among these four systems, the magnetic field resonance system has drawn particular attention. In the magnetic field resonance system, there has been proposed a “1-to-N” power supply system in which a power transmission device performs wireless power transmission to a plurality of power receiving devices, taking advantage of this long power transmission distance (refer to Japanese Patent Application Laid-Open No. 2009-136132, for example).
In the technique discussed in Japanese Patent Application Laid-Open No. 2009-136132, a power transmission device transmits a certain pulse signal while it is in a standby mode where the power transmission device does not supply power, to search for any power receiving device approaching the power transmission device within several meters therefrom. If any power receiving device transmits its unique ID to the power transmission device, the power transmission device determines whether the transmission source of the unique ID is a power supply target power receiving device. If the power receiving device is a power supply target, the power transmission device supplies power to that power receiving device. At the time, the power transmission device can transmit a unique code to the wireless power receiving device to individually receive an amount of charge and a state of the device from the wireless power receiving device.
The power transmission area within which power can be transmitted from a power transmission device is limited. Therefore, in a case of a portable power receiving device, when the power transmission device transmits power to the power receiving device, the user has to move the power receiving device into the power transmission area. Further, even if the power receiving device is within the power transmission area, an obstacle between the power transmission device and the power receiving device may block power to the power transmission device.
However, it is difficult for the user to determine to which position the power receiving device has to be moved in order to improve the power transmission efficiency. Consequently, in some cases, power transmission is performed in a low transmission efficiency state, so that there has been the problem of wasteful power consumption.